In wireless communication system, multiple antenna techniques are commonly used. According to their basic principles, these techniques can be classified into three categories: spatial multiplexing, spatial diversity and beam forming.
The core idea of the spatial multiplexing technique lies in that a sending end and a receiving end respectively use a plurality of antennas arranged in proper positions or with different polarities to form a plurality of channels independent with each other between the sending end and the receiving end. As a result, the sending end can send different data to different channels and the receiving end can receive these data respectively to acquire greater spectral efficiency.
The core idea of the spatial diversity technique lies in that a transmitter and a receiver use a plurality of antennas arranged in proper positions or with different polarities to produce an independent fading channel. The sending end encodes a same signal and sends it to different channels to achieve the spatial diversity. Due to the employment of the coding technique, the spatial diversity technique can obtain some coding gain in addition to diversity gain.
The core idea of the beam forming technique lies in that a transmitter and a receiver use a plurality of antennas arranged in proper positions to enable the sending end and the receiving end to get channels with the same or similar fading characteristics. The difference among the different channels lies in different routes, according to which the receiving end can get the Direction of Arrivals (DOA) of a signal conveniently and processing gain can be obtained by adjusting the phase of the receiving antenna and making the array antennas point at the coming direction of the signal.
The spatial multiplexing technique is usually applicable to the condition of a good-quality channel; the spatial diversity technique is applicable to a complex environment of multi-path fading; and the beam forming technique is applicable to an open and outdoor channel environment with a main path. However, due to the different basic principles employed respectively, it is difficult to use these three techniques in a multiple antenna system at the same time. Therefore, only one of the above three multiple antenna systems is usually applied in wireless communication system.
With people's increasing demand on wireless mobile services, it becomes a goal pursued by wireless communication system to acquire the greatest performance by different techniques in different scenarios. Therefore, a multiple antenna mode control method is in urgent need to enable wireless communication system to cover a mobile Station and an Access Point with the spatial multiplexing, the spatial diversity and the beam forming techniques at the same time, and to allow the sending and the receiving ends to select a suitable multiple antenna mode for transmitting data according to the specific channel environment.